374 



hydrogen, to which many travellers attribute 

 the smell perceived amid mangroves. The 

 decomposition of the earthy and alkaline sul- 

 phats, and their transition to the state of sul- 

 phurets, no doubt may favour this disengage- 

 ment in many littoral and marine plants ; for 

 instance, in the fuci : but I am rather inclined 

 to think, that the rhizophora, the avicennia, 

 and the conoearpus, augment the insalubrity 

 of the air by the animal matter, which they 

 contain jointly with tannin. These shrubs be- 

 long to the three natural families of the loran- 

 theae, Ijhe combretacese # , and the pyrenaceae, in 

 which the astringent principle abounds ; and I 

 have already observed, that this principle ac- 

 companies gelatin, even in the bark of beech, 

 alder and nut-trees f . 



Besides, a thick wood covering marshy grounds 

 would diffuse noxious exhalations in the atmos- 

 phere, were it composed of trees which in them- 

 selves have no deleterious properties. Wher- 

 ever mangroves grow on the seashore, the beach 

 is covered with an infinite number of molluscae 

 and insects. These animals love the shade, and 

 a faint light ; and they find themselves sheltered 

 from the shock of the waves amid this scaf- 

 folding of thick and intertwining roots, which 



* Rob. Brown, Flor. Nov. Holl. Prod., vol. i, p. 351. 

 + Vauquelin, Annal. du Mus., T. xv, p. 77. 



